1. Field of the Invention
The present invention relates to a plasma etching method and a storage medium, and more particularly to an plasma etching method in which a CwFx (x and y are predetermined natural numbers)-based low-dielectric interlayer insulation film and a metallic layer or a metal-containing layer are exposed to plasma at the same time.
2. Description of the Related Art
In recent years, in a semiconductor device manufactured from a semiconductor wafer through a CVD process, plasma etching, or the like, a low-dielectric interlayer insulation film is used so as to lower parasitic capacitance due to insulation films between wires, and also, copper wiring is used so as to lower wiring resistance. In particular, as a low-dielectric interlayer insulation film, for example, a porous SiO2 film, SiOC film, or SOG (Spin on Glass) film (for example, a film formed of hydrogen silsesquioxane (HSQ) or methyl silsesquioxane (MSQ)) is used.
An SiC layer, an SiCN layer, and so on are formed as an etching stopper layer on copper wiring so as to prevent inadvertent etching of the copper wiring. When a via hole that reaches the copper wiring is to be formed, these layers such as the SiC layer are removed by etching. In etching of an SiC layer or the like, plasma generated from a single gas of a fluorine compound or a mixed gas of a fluorine compound gas (for example, CF4 gas or CH2F2 gas) and N2 gas has been conventionally used. Here, if the mixed gas is used, the flow rate of the N2 gas is set to be lower than the flow rate of the fluorine compound gas (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2002-110644).
An SOG film is a film that is formed by coating a fluid material and ensures a low dielectric constant by increasing porosity, and therefore, the SOG film has the problem of having a low mechanical strength. Thus, in recent years, it has been considered that a CwFx-based organic film is used as a low-dielectric interlayer insulation film having a high mechanical strength.
However, the inventors of the present invention and others etched an SiCN layer using plasma generated from a mixed gas of CF4 gas and N2 gas in a semiconductor wafer having a CwFx-based interlayer insulation film, an SiCN layer, and copper wiring before putting a CwFx-based organic film to practical use, and found that, after the SiCN layer was removed to expose the copper wiring through the etching, residues became attached to bottoms and sides of via holes reaching the copper wiring and trenches formed in an interlayer insulation film. These residues cause short-circuiting and capacitance change in a semiconductor device, and thus have to be prevented from being produced.